1. Field of the Invention
This invention relates generally to golf club shaft manufacturing procedures, and more particularly to an improved shaft manufacturing procedure that allows a golf club shaft that is not uniformly tapered to be easily manufactured with standard table-rolling equipment rather than requiring the use of expensive, specialty tools.
2. Description of Related Art
Conventional golf club shafts generally have an elongate, cylindrical shape and are uniformly tapered along the length so that the smallest diameter of the shaft is at the neck, where the club head is attached, and the largest diameter of the shaft is at the opposing, handle end where the shaft is typically gripped.
The standard method for making evenly tapered golf club shafts is commonly known as the table-rolled method. This method consists generally of laying one or more graphite flags in a bias pattern on a rolling table, and then rolling the flags around a mandrel. One or more straight-pattern flags are then hand-rolled around the mandrel. When the appropriate number of flags have been rolled around the mandrel to achieve the desired strength and torque of the shaft, shrink tape is then placed around the rolled mandrel, and the entire assembly is put in a curing oven. When the graphite has been thoroughly cured, the mandrel is extracted and the shrink wrap is removed, leaving a solid, hollow golf club shaft having an interior that conforms to the shape of the mandrel. The shaft is them cut to the appropriate length, sanded and finished as desired.
However, there is currently a trend in the golf industry to manufacture golf club shafts that are not uniformly tapered, but rather have at least one outwardly curved protrusion near the handle end of the shaft. Unfortunately, the standard table-rolled method cannot be used to create such a shaft, since the shafts manufactured in this way must continually taper in order to allow for the extraction of the mandrel.
U.S. Pat. No. 5,316,299 issued to Feche et al. discloses a shaft having such a protrusion, and French patent 91 12937 discloses a procedure for creating such a shaft. As disclosed, the process for making a non-uniformly tapered shaft requires that an air bladder be used in place of a mandrel. When inflated, the air bladder has a generally elongate, tapered shape with the desired outwardly extending protrusion. Once the air bladder has been appropriately covered with layers of graphite and cured, the air is released from the air bladder and the bladder is simply extracted from the cured golf club shaft. Both the interior and the exterior of the resulting shaft conform to the shape of the inflated air bladder. Unfortunately, as disclosed this process has many significant drawbacks and limitations. Most importantly, most golf club shaft manufacturers are equipped to manufacture shafts using mandrels and standard table-rolling procedures, and thus cannot easily incorporate the air-bladder method into their current modes of operation. In addition to the air bladder, this manufacturing process also requires specialized equipment that costs approximately $100,000 per machine.
In an attempt to avoid the expense associated with the above processes, a shaft with an outward curvature has been manufactured using traditional table-rolled techniques. In order to accomplish this, graphite flags are rolled around the mandrel as described above, and then additional layers of graphite are simply added to the exterior of the mandrel to create an outward protrusion on the shaft. This produces a shaft having an interior that is hollow in a uniformly tapered manner, and an exterior that has a protrusion. However, while this method is less expensive because standard table-rolling equipment is employed, the resulting shaft is up to 20 grams heavier than those made with an air bladder, which is a significant disadvantage in achieving maximum golf swing performance.
Thus there is a clear need for an improved golf club manufacturing process that allows a shaft that is not uniformly tapered to be easily created using traditional table-rolling equipment without increasing the weight of the resultant shaft. Such a process would reduce manufacturing costs and further reduce the weight of the shaft. The present inventive manufacturing process fulfills these needs and provides further related advantages as described in the following summary.